Document EP-A-0 646 735 describes an example of a hydraulic antivibration support of the above-specified type, in which the free edges of the base of the elastomer body are formed by two tabs of the perforated insert which are covered in elastomer and which are interposed between the zones where the cover is fixed to the plate.
As a result, when such antivibration supports are in use, the elastomer layers covering said tabs of the perforated insert can creep under the effect of repeated forces applied by the cover, and that can lead to leaks.